Rotary driving tool with variable pitch spring



y 13, 1965 R. c. BENNETT 3,194,370

ROTARY DRIVING TOOL WITH VARIABLE PITCH SPRING Filed July 25, 1962 IN VEN TOR. fiazz/Zarza 6562222622,

\N MN 7 mm Q Q Q %w\ Sw QM N7 r A 6 3 m mm 3 k w 2. 47 /V w\ RN NM 3 in. v h 55 W a 3 aw Q Q KQSN Q Q. fw Q United States Patent 3,194,376) RGTARY DRE/ENG TUUL WlllH VARHAELE Pl'lCl-l SPRING Rowland C. Bennett, Palatine, Ill, assignor to Eliril Qorporation, Chicago, lll., a corporation of Delaware Filed July 25, 1962, Ser. No. 212,296 4 Claims. (U. 192*55) The present invention relates to a spring and, more particularly, to a variable pitch spring for use in a rotary driving tool.

In rotary driving tools, such as the one disclosed in US. Patent No. 3,020,789, dated February 13, 1962, a standard compression coil spring normally used therein as a torque control spring is effective for rotary driving opera tions within a specified range of work, for instance from 18 to 50 inch-pounds. For rotary drivin operations above and below such work limitations, it has been necessary in the past for the operator to shut down the tool and substitute springs having greater or lesser compression ratings for the standard spring therein, thus resulting in considerable undesirable tool down-time and extra work on the part of the operator.

It is, therefore, an important object of the present invention to provide a new and improved compression coil spring wherein the pitch of the spring varies along its length, which variable pitch spring is adapted for use in such a rotary driving tool to permit efficient operation and sensitive adjustment of same under both relatively light and relatively heavy driving conditions within a considerably extended work range, for instance from 1 to 100 inchpounds as compared with a work range of 18 to 50 inchpounds for a standard non-variable pitch coil spring or" comparable size.

Another important object of the present invention is to provide a new and improved variable pitch compression spring of the character described having both soft and hard coils and having a generally hour-glass configuration to prevent swelling of the center of the spring when same is compressed.

A further object of the present invention is to provide a new and improved variable pitch compression spring of the character described for use in a rotary driving tool whereby to eliminate the wasteful down-time normally required for an operator to change compression springs when switching over from exceedingly light driving operations to heavy industrial driving operations and vice versa.

Certain other obiects of the invention will, in part, be obvious, and will in part appear ereinafter.

For a more complete understanding of the nature and scope of the invention reference may now be had to the accompanying drawings wherein:

PEG. 1 is a side elevational view of a variable pitch spring embodying a preferred form of the invention and having a generally hour-glass configuration; and

FlG. 2 is a central section taken through a rotary driving tool utilizing the variable pitch compression spring of PEG. 1.

As illustrated in H6. 1, a variable pitch spring ill embodying the invention is characterized by a series of coils including opposite end coils ii and 12 and intermediate or center coils 13 and 14. The ends of the end coils and 12 may be charnfered in a known manner. As illustrated, the pitch or distance x between corresponding points on the coils l2 and 14 at one end of the spring fill is less than the pitch or distance y between the coils 1t and 13 at the opposite end of the spring lil whereby the coil compression spring it) is provided with variable pitch characteristics. Coil 1.3 having the greater pitch acts as a hard coil and is adapted particularly for heavy driving operations and coil 14 having the lesser pitch acts as a soft coil ddh ldld Patented July 13, E955 and is adapted particularly for light driving operations. The variable pitch spring ill is effective, for instance, within a range of 1 to 100 inch-pounds of work as compared with a of 18 to inch-pounds of work for a standard non-variable pitch compression spring having comparable physical characteristics. The actual work-load range for the variable pitch spring 1%) is determined, of course, by the particular physical characteristics thereof, such as the spring material, the free length of the spring, the wire and coil diameters, the number of coils, etc.

Compression coil springs normally swell or bulge at their centers when fully compressed, which characteristics may be extremely undesirable in certain circumstances, as where the spring is closely confined and any swelling might result in rubbing or interference with the normal operation thereof. Therefore, as illustrated in FIG. 1, the outer diameters of the coils of the spring ill decrease progressively in directions inwardly of the opposite end coils l1 and 12 whereby the spring 1d has a generally hour-glass configuration or shape. Thus when the spring ill is fully compressed, the center coils l3 and 14 do not swell or bulge outwardly so far that they extend beyond the outer diameter of the end coils 11 and 12.

The variable pitch compression spring 1% is particularly well adapted for use in a rotary driving tool such as the one which is fully disclosed in detail in US. Patent No. 3,626,789, dated February 13, 1962. Brieii as illustrated in FIG. 2, such a tool includes a sleeve-like casing 263 which is mounted at its rear end on an adapter or front end portion 21 of a rotary power tool of a known type (not shown) with a drive shaft 22 thereof projecting forwardly into the casing 25) with its projecting end being supported in a ball bearing 23. A sleeve member 24 is mounted in the front end of the casing Ztl for rotation relative thereto, for a purpose which will be described hereinafter, with a jam or locking nut or ring 25 being provided for locking the sleeve member 24 in an adjusted position. A finder sheath in having an outwardly flared forward end 27, which serves as a guide for placement thereof over a fastener such as a screw, is telescopically mounted in the forward end of the sleeve 24 with a spring 23 normally urging the finder sheath 26 in a forward direction relative thereto. The sheath 26 is retained in the sleeve 24 by a lmown type spring detent 33. An adjusting nut 36 is threadedly mounted on the inner or rear end of the sleeve 24-, which nut Ed is held against rotation relative to the casing by a detented portion 31 of the casing 26 which extends into a longitudinally extending slot 32 formed in the adjusting nut A torque control clutch 34- which is rotatably mounted in the rear portion of the casing includes a powerreceiving clutch member 35 which is drivingly connected to the forward end of the power tool drive shaft 2-2 by a lniown type hex drive arrangement and a driven clutch ember 36 having a seri s of clutch teeth 37 on its forward end. Cam means for drivingly interconnecting the power-receiving clutch member 35 and the driven clutch member 36 are preferably in the form of a series of bearing balls 38 which are disposed therebetween and seated in specially designed recesses 39 and 46 formed therein, respective.y, as described in detail in the previously referred to Patent No. 3,020,789. lonnally the driven clutch member 35 is in a closed position and juxtaposed to the clutch member 35 in driving engagement therewith, as illustrated in FIG. 2. It will be seen that when torque is applied between the clutch members 35 and 36 there will be a tendency for the bearing balls 33 to cam out of the recesses 4% since they are somewhat shallower and of a different shape than the recesses 39. This camrning tendency increases as the torque increases.

in addition to the torque control clutch 34, a positive engagement clutch 4-2 is provided including a collar-like I control clutch 34,

member 43 which is keyed on a spindle 44 by a ball key- 45 for axial movement relative thereto and which is-provided at its rear or inner end with a series of clutch teeth 46 which-are adapted for engagement with the tending through the driven clutch member 36, which is.

centrally bored, and into a central bore formed inthe power-receiving clutch member 35, the spindle'd 'being freely rotatable relative to the clutch members 35 and- 36. A driving bit 49 has its rear end mounted in a socket 50 which is formed in the front end of the spindle 4dfor-rotation therewith with a known type ball detent 52 and a garter-like clip 53 being provided to releasably Y retain the bit 49 in the socket 5%.

A compression spring 54 normally'urges the collarlike member 43 into its rearwardmostposition relative to the spindle 44, as determined by the ball key 45', in which position the clutch teeth 46 thereon are vspaced forwardly of and not engaged with the clutch teeth 37 on the driven clutch member 36 when same is juxtaposed to the power-receiving clutch 'member 35. The

variable pitch torque control spring 16 of the invention, 4

previously described in detail herein, has its end coil 11 seated against-the rear surface of the adjusting nut and its opposite end coil 12 seated against an annular seat member 5:3 which abuts against the front end of 36 =istnormally urged rearwardly into driving engage.-

ment with the power-receiving clutch member 3 5.

In use with the driving tool motor operating, the finder sheath 26 is pressed against a fastener member to be drivingly rotated, such as a screw, the head thereof being seated in centered relationship in the outwardly flared s end 27 of the sheath 26, whereby the sheath 26 is shifted tip of the bit 49 is engaged in a recess in the screw head.

r arw dy against the force of the Spring 28 untilrthe range of possibletorque'values for disengagement 'ofthe" During the foregoing, the switch members '35 and 36 ofthe torque control clutch 34 have been rotating but the other parts have remained stationary. Further pressure against the screw causes rearward axial movement of the spindle 44, as a result of the engagement of the rear end of the bit 49 against the inner end of the socketdii tive clutch 42 thus'engagedthe spindle 44 and thebit 49 are rotatablydriven to drive the screw or other fastener.

The. driving continues until such time. as the fastener clutch teeth ddare completelydisengaged .fromsthe clutch teeth;37 on the vdriven 'clutch' member 36.; s As is described and illustrated in detail in US. Patent No.

3,620,789, previously referred to hereinglatchlballs (not shown in FIG. 2), for instance may be provided to auto-.

matically retain the, collar-like member 43 'in'its. forward-J 1y shifted position outoi driving engagementwwith the,

torque control fclutch134 afterthe instantaneous .disena disengaged condition after the predetermined torque value 1 has been exceeded whereby to prevent further: driving :of the fastenencomprises; no part of the-present invention and that, therefore the structure and-operation or .the

rotary driving tool have only been briefly described herein;

7 The :cornpressionof the'torque control'spring l0 and: J thus the predetermined torque. .valueyatwhich the torque; control clutch 34 is .to'be disengagedmay be varied. by the adjusting nut 3t Thelongitudinal position of the" adjusting nut 30 relative to the casing 29 may be readily adjusted by firstsloosening thelocking ring 25' afterwhich the sleeve 24-isirotated-by' means of wrench-engageable' flats 58 provided on the forwardend"thereof-whereby t the adjustingn'ut :39, which :isirestrainedragainstrotation V relative to the. casing 29 by therdetented portion 31" thereof, is adjusted longitudinallyrof' thecasing 2d; to:increase I or 7 decrease 5 the compression 50f the torque control spring ill.

When a standard non-variable compression coil spring is used 'as a torque control spring in such a rotary driving tool, the range of compression of the spring and thus [the torque control clutch 34 are relatively limited? Thus, for

both relatively light driving operationsyand. :relatively heavy industrial driving operations, it hasbeen necessary, in the past,;for' an operator to shut downthe tool, dis assemble same and substitute a spring having a lesser or greater compression rating than that of the, standard coil; spring normally provided in a rotary drivingtool ofthis I-lowever, vasv previously described in. detail herein, the variable pitch compression coil spring rlil'of the present mventronprovrdes an extended;range Eof-itorque control v 7 spring compression and thus an extended range of'possible is driven to the point where the torque exceeds the pre: 7 determined torque value for which the torc tie control.

clutch 34 has been set, this torque value being determinedby the compression of the torque control spring .10 Whichis adjustable by the adjusting nut 3%) in a manner which will be described. When this predetermined torque value is exceeded, the bearing balls 38 cam out of the shallow recesses 4% in the driven clutch member 36' whereby the driven clutch member 36 is shifted forwardly against the force of the torque control spring 1th with recesses 4i) therein whereby to again engage the torque However, the collar-like member 53, is retained in its forwardly shifted position whereby its' torque values for disengagement of the torquevcontroh clutch 34 whereby relatively 'light andrelativ'ely heavy driving operations,,as wellas normal driving operations, may be efticiently'handledby the rotary driving .tool-with-. outthe necessityof the operator. shutting down the tool and changing the torque control spring t herein; It is noted that anextended work-load-range ifor ;a typical variable; pitch compression coil springiof the invention as compared with the vwork-loadTangent a, standard non, variable pitch compression coilspring ,of comparableisirze' has previously been set forth herein: It is iurther rioted that the hard or greater pitch coil 13 ofjthe variable pitch a torque control spring 1% particularlyfacilitates extremely;

sensitive Vcontrol. of the compression Ethereof' andthus permits fine adjustment of a desired-predeterminedtorque value for disengagement of the torque control clutch 34; f:

It will be understood that certain changes may be made in the construction ordesign'of the variable pitclhgcoil;

, spring'ndisclosed herein" Without departing. from the' spirit and scope-ofth e invention as defined in the appended claims.

torque control clutch 34 rotating andzall of the other. parts being stationary. Upon frelease. of the; pressure- I claim:

1. In a rotary driving tool characterized by a sleeve-like casing, by a spindle therein having a driver supporting means at its forward end, by a driven clutch member connectable to said spindle for rotatably driving same, by a rotatable power-receiving clutch member, by completely disengageable camming means normally directly interconnecting said clutch members and tending to separate said driven clutch member from said power-receiving clutch member at a predetermined torque value, and by torque value adjusting means, the improvement which comprises, a compression coil spring within said casing characterized by a series of coils with one or more coils at one end thereof having a greater pitch than the pitch of one or more coils at the opposite end thereof whereby said coils at said one end are adapted particularly for heavy driving conditions and said coils at said opposite end are adapted particularly for light driving conditions, said spring urging said driven clutch member into driving engagement with said power-receiving clutch member and resisting separation by said camming means until a predetermined torque value is exceeded, the degree of compression of said spring and thus said predetermined torque value being adjustable by said torque value adjusting means through a relatively wide range due to the variable pitch characteristics of said spring.

2. In a rotary driving tool characterized by a sleeve-like casing, by a spindle therein having a driver supporting means at its forward end, by a driven clutch member connectable to said spindle for rotatably driving same, by

a rotatable power-receiving clutch member, by completely disengageable camming means normally directly interconnecting said clutch members and tending to separate said driven clutch member from said power-receiving clutch member at a predetermined torque value, and by torque value adjusting means, the improvement which comprises, a compression coil spring within said casing characterized by a series of coils with one or more coils at one end thereof having a greater pitch than that of one or more coils at the opposite end thereof whereby said coils having the greater pitch are adapted particularly for heavy driving conditions and said coils having the lesser pitch are adapted particularly for light driving conditions, the outer diameters of all of the coils of said spring decreasing progressively from the opposite ends of the spring in wardly toward the center thereof whereby said variable pitch spring has a slightly hour-glass configuration, said spring urging said driven clutch member into driving engagement with said power-receiving clutch member and resisting separation by said camming means until a predetermined torque value is exceeded, the degree of compression of said spring and thus said predetermined torque value being adjustable by said torque value adjusting means through a relatively wide range due to the variable pitch characteristics of said spring.

3. In a rotary driving tool characterized by a sleeve-like casing, by a spindle therein having driver supporting means at its forward end, by a driven clutch member connectable to said spindle for rotatably driving same, by a rotatable power-receiving clutch member, by completely disengageable camming means normally directly interconnecting said clutch members and tending to separate said driven clutch member from said power-receiving clutch member at a predetermined torque value, and by torque Cir value adjusting means, the improvement which comprises, a compression coil spring within said casing characterized by a series of coils wherein the distance between adjacent coils at one end of the spring is substantially greater than the distance between adjacent coils at the opposite end of the spring with said coils at said one end of said spring serving as hard coils and being adapted particularly for heavy driving conditions and with said coils at said opposite end of said spring serving as soft coils and being adapted particularly for light driving conditions, said spring urging said driven clutch member into driving engagement with said power-receiving clutch member and resisting separation by said camming means until a predetermined torque value is exceeded, the degree of compression of said spring and thus said predetermined torque value being adjustable by said torque value adjusting means through a relatively wide range due to said hard and soft coils of said spring.

4. In a rotary driving tool characterized by a sleeve-like casing, by a spindle therein having a driver supporting means at its forward end, by a driven clutch member connectable to said spindle for rotatably driving same, by a rotatable power-receiving clutch member, by completely disengageable camming means normally directly interconnecting said clutch members and tending to separate said driven clutch member from said power-receiving clutch member at a predetermined torque value, and by torque value adjusting means, the improvement which comprises, a compression coil spring within said casing characterized by a series of coils wherein the distance between adjacent coils at one end of the spring is substantially greater than the distance between adjacent coils at the opposite end of the spring with said coils at said one end of said spring serving as hard coils and being adapted particularly for heavy driving conditions and with said coils at said opposite end of said spring serving as soft coils and being adapted particularly for light driving conditions, said spring urging said driven clutch member into driving engagement with said power-receiving clutch member and resisting separation by said camming means until a predetermined torque value is exceeded, the degree of compression of said spring and thus said predetermined torque value being adjustable by said torque value adjusting means through a relatively wide range due to said hard and soft coils of said spring, the outer diameters of all of the coils of said spring decreasing progressively from the opposite ends of the spring inwardly toward the longitudinal center thereof whereby said spring has a generally hour-glass configuration.

References Cite-d by the Examiner UNITED STATES PATENTS 2,161,165 6/39 Hirschman 2676l 2,257,759 10/41 Niemann 6429 2,387,264 10/45 Holland 267-61 2,728,252 12/55 Connell 192-56 3,020,789 2/ 62 Etzkorn 8152 FOREIGN PATENTS 508,271 7/20 France.

206,316 11/23 Great Britain.

402,792 12/33 Great Britain.

DAVID J. WILLIAMOWSKY, Primary Examiner. 

1. IN A ROTARY DRIVING TOOL CHARACTERIZED BY A SLEEVE-LIKE CASING BY A SPINDLE THEREIN HAVING A DRIVER SUPPORTING MEANS AT ITS FORWARD END, BY A DRIVEN CLUTCH SUPPORTING CONNECTABLE TO SAID SPINDLE FOR ROTATABLY DRIVING SAME, BY A ROTATABLE POWER-RECEIVING CLUTCH MEMBER, BY COMPLETELY DISENGEABLE CAMMING MEANS NORMALLY DIRECTLY INTERCONNECTING SAID CLUTCH MEMBERS AND TENDING TO SEPARATE SAID DRIVEN CLUTCH MEMBER FROM SAID POWER-RECEIVING CLUTCH MEMBER AT A PREDETERMINED TORQUE VALUE, AND BY TORQUE VALUE ADJUSTING MEANS, THE IMPROVEMENT WHICH COMPRISES, A COMPRESSION COIL SPRING WITHIN SAID CASING CHARACTERIZED BY A SERIES OF COILS WITH ONE OR MORE COILS AT ONE END THEREOF HAVING A GREATER PITCH THAN THE PITCH OF ONE OR MORE COILS AT THE OPPOSITE END THEREOF WHEREBY SAID COILS AT SAID ONE END ARE ADAPTED PARTICULARLY FOR HEAVY DRIVING CONDITIONS AND SAID COILS AT SAID OPPOSITE END ARE ADAPTED PARTICULARLY FOR LIGHT DRIVING CONDITIONS, SAID SPRING URGING SAID DRIVEN CLUTCH MEMBER INTO DRIVING ENGAGEMENT 